On Mar 25, 2009, at 12:09 AM, Dave Toll wrote:

> Hello list
>
>
>
> I have been trying to understand how shared cache works under the
> covers, and how a custom VFS should behave when shared cache is  
> enabled
> - can anyone confirm this assumption:
>
>
>
> Journal file handles (opened with SQLITE_OPEN_EXCLUSIVE) are shared
> between database connections opened on the same DB filename. Access  
> to a
> journal file handle is serialised through the BTShared mutex of the
> owning database - there is no explicit locking performed on journal
> files.

That is correct. SQLite will serialize calls on a single file-handle
(sqlite3_file*). You do not need a mutex for each file-handle in the
OS layer.

Dan.



>
>
>
>
> Cheers,
>
> Dave.
>
>
>
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